LED backlighting for displays

ABSTRACT

A display system including a display panel having a first major surface and a second major surface and a lighting system adapted to provide uniform luminance proximal to the display panel is disclosed. The lighting system includes an illuminating substrate having a first major surface with reflective coating and a second major surface. The illuminating substrate defines an array of mounting holes, each hole occupied by an LED module. An array of light emitting diode (LED) modules are affixed to the illuminating substrate, each module including at least one light emitting diode adapted to emit light. The lighting system can also include a diffusant layer which can be optically coupled to the illuminating substrate by soft optical gel and is placed close to or made to contact the display panel. The optical gel may contain phosphors or other optical substance for added optical performance to the lighting system. The diffusant layer has beveled edges at critical angle of refraction or coated with reflective material to minimize light loss at its edges. Each of the LED modules includes at least one LED chip, conductive traces connected to the LED chip and a heat sink.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 11/153,724, filed Jun. 14, 2005 now U.S. Pat. No.7,980,743, the entire content of which is hereby incorporated byreference herein.

BACKGROUND

The present invention relates to the field of display devices, and moreparticularly to lighting of flat panel display devices such as liquidcrystal display (LCD) devices.

LCD devices are widely used in flat panel displays for computer anddisplay monitors, televisions, bill boards, road signs, and otherapplications. In some applications, for example as a computer displayfor notebook computers, LCD devices are desirable because they are muchthinner and lighter than alternatives such as, for example, CRT (cathoderay tube) displays.

An LCD panel is generally (but not necessarily) configured as a thinrectangular panel having a first major surface (its “front”) and asecond major surface (its “back”). As a rectangular panel, it has fouredges, or sides, defining the boundaries of the LCD panel. The LCD panelincludes a number of sub-layers such as a liquid crystal layer and aplurality of optical filter layers. An LCD screen can consist ofthousands or millions of pixels covering the screen; manipulation ofthese pixels, in combination of a lighting subsystem, results in thedisplaying effect.

As is known to those skilled in the art, an LCD does not emit light;rather, the displaying effect is produce by control of light from a sideor backside lighting subsystem that provides light to the LCD panel.Thus, the quality of the displayed image depends on, in part, thequality and the wavelengths of light from the lighting subsystem(typically on the backside of the LCD panel).

A common backlit LCD device includes an LCD panel with one or morefluorescent tubes running proximal to one or more edges of the LCDpanel. Light pipes guide light from the fluorescent tubes or any lightsource to the back surface of the LCD panel. Thus, the LCD panel isbacklit allowing a viewer to more easily view, from the front surface,the information on the LCD panel. Unfortunately, such edge lightingsystem is inefficient with up to 50% or more of the light being lost.See, for example, U.S. Pat. No. 6,672,734 B2, U.S. Pat. No. 6,768,525B2, and U.S. Pat. No. 6,844,903 B2.

In an alternative design, an array of fluorescent tubes are placed nearthe back surface of the LCD panel allowing direct illumination of theback surface of the LCD panel thereby eliminating the need for the lightpipes and increasing the efficiency of the lighting system. However,fluorescent light does not deliver all the primarily colors—Red, Greenand Blue—which can then be combined to yield millions of secondarycolors for the display. That is, the images displayed are not trulynatural and brilliant as desired for some applications.

Consequently, there remains a need for an improved system forilluminating flat panel displays that overcomes or alleviates theshortcomings of the prior art devices. Semiconductor light emittingdevices, such as Light Emitting Diode (LED) devices, also may be usedfor edge illumination of a planar array of LCD devices. For example,U.S. patent application Ser. No. 10/898,608, filed Jul. 23, 2004,entitled Reflective Optical Elements for Semiconductor Light EmittingDevices, to co-inventor Negley, and assigned to the assignee of thepresent invention, the disclosure of which is hereby incorporated hereinby reference in its entirety as if set forth fully herein, describesside emission LEDs that may be used for large area LCD and/or televisionbacklighting.

SUMMARY

The need is met by the present invention. In one embodiment of thepresent invention, a display system includes a display panel having afirst major surface and a second major surface and a lighting systemadapted to provide light proximal to the second major surface of thedisplay panel. The lighting system includes an illuminating substratedefining an array of mounting holes and an array of light emitting diode(LED) modules, each module occupying a mounting hole of the array ofmounting holes.

The illuminating substrate includes a substrate core having a firstmajor surface and a second major surface opposite the first majorsurface and a light reflective layer covering at least a portion of thefirst major surface of the substrate core. The light reflective layerincludes at least one member from a group consisting of silver, gold,aluminum, and reflective paint or coating, for example, Barium Sulfateor Titanium Dioxide paint. The light reflective layer can alsoincorporate optical gratings or textures of its surface to scatter lightrays that are reflected from it. The illuminating substrate furtherincludes circuit elements on the second major surface of the substratecore.

The display system may also include a diffusant layer between thedisplay panel and the illuminating substrate. The diffusant layerreceives light emitted by individual emitters of the LED modules anddistributes it uniformly with minimal loss. It is optically coupled withthe illuminating substrate via optical gel to minimize losses of lightat the interface. Outer edges of the diffusant layer are made to a bevelangle with specular surface finishes to minimize light loss from theedges. The bevel angle can be close to critical refractive angle of themedium to promote light rays being reflected by TIR (Total InternalRefraction). Alternatively, or in combination, the edges can havereflective coating such as Barium Sulfate or Titanium Oxide paint toprevent light rays escaping through the edges.

Each of the LED modules includes one or more LED chips and conductivetraces connected to the LED chips. The circuit elements are adapted toconnect to the conductive traces of the LED module. The LED module mayalso include heat sink for improved heat dispersion.

The display panel, depending on technology and implementation, caninclude a plurality of sub-layers such as, for example, a first filtersub-layer, a thin film transistor sub-layer, a liquid crystal sub-layer,and a second filter sub-layer.

Other aspects and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, illustrating by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded perspective view of an apparatus according to oneembodiment of the present invention;

FIG. 1B is a portion of the view of FIG. 1 in greater detail;

FIG. 2A is view of the apparatus of FIG. 1 from front of the apparatus;

FIG. 2B is view of the apparatus of FIG. 1 from rear of the apparatus;

FIG. 2C is a cutaway side view of the apparatus of FIGS. 2A and 2B cutalong line 2C-2C of FIGS. 2A and 2B;

FIG. 2D is a more detailed view of a portion of the cutaway side view ofFIG. 2C;

FIG. 2E is a simplified diagram of another portion of the display system100 of FIGS. 2A through 2D; and

FIG. 3 is a perspective view of a LED module of FIGS. 1A through 2D.

DETAILED DESCRIPTION

The present invention will now be described with reference to the FIGS.1A through 4, which illustrate various embodiments of the presentinvention. As illustrated in the Figures, some sizes of structures orportions are exaggerated relative to other structures or portions forillustrative purposes and, thus, are provided to illustrate the generalstructures of the present invention. Furthermore, various aspects of thepresent invention are described with reference to a structure or aportion being formed on other structures, portions, or both. As will beappreciated by those of skill in the art, references to a structurebeing formed “on” or “above” another structure or portion contemplatesthat additional structure, portion, or both may intervene. References toa structure or a portion being formed “on” another structure or portionwithout an intervening structure or portion are described herein asbeing formed “directly on” the structure or portion.

Furthermore, relative terms such as “on” or “above” are used herein todescribe one structure's or portion's relationship to another structureor portion as illustrated in the Figures. It will be understood thatrelative terms such as “on” or “above” are intended to encompassdifferent orientations of the device in addition to the orientationdepicted in the Figures. For example, if the device in the Figures isturned over, structure or portion described as “above” other structuresor portions would now be oriented “below” the other structures orportions. Likewise, if the device in the Figures is rotated along anaxis, structure or portion described as “above” other structures orportions would now be oriented “next to” or “left of” the otherstructures or portions. Like numbers refer to like elements throughout.

As shown in the figures for the purposes of illustration, embodiments ofthe present invention are exemplified by a display system includes adisplay panel having a first major surface and a second major surfaceand a lighting system adapted to provide light proximal to the secondmajor surface of the display panel. The lighting system includes anilluminating substrate defining an array of mounting holes and an arrayof light emitting diode (LED) modules, each module occupying a mountinghole of the array of mounting holes. The lighting system can alsoinclude a diffusant layer which is placed between the display panel andthe illuminating substrate to achieve high luminous efficiency anduniform luminance.

In the present invention, LEDs (light emitting diodes) of the primarycolors (Red, Green and Blue) are used to illuminate a display panel witha complete spectrum of colors by varying the electrical currents thatdrive the LED's. Inside the lighting system, an optical gel (rather thanan air gap) couples the illuminating substrate to the diffusant layer tominimize light loss at the interface. Further, the illuminatingsubstrate incorporates a highly reflective, grated or textured surfacefacing the diffusant layer to diffuse and reflect light rays to achievehigh luminous efficiency and a uniform luminance. In addition, the edgesof the diffusant layer are beveled at an angle and made to specularfinish or coated with reflective material such that light rays that hitthe edge surface are less likely to escape from the medium of thediffusant layer but is more likely to be reflected and directed towardsthe front side of the diffusant layer.

Details

FIG. 1A is a partially exploded perspective view of a display system 100according to one embodiment of the present invention. FIG. 1B is aportion 102 of the display system 100 in greater detail. The displaysystem 100 is, for example, a flat-panel computer monitor. Referring toFIGS. 1A and 1B, the display system 100 has a first major surface 101(front) and a second major surface 103 (rear). The display system 100 isviewed from its front 101.

FIG. 2A is a view of the display system 100 from its front 101. FIG. 2Bis a view of the display system 100 from its rear 103. FIG. 2C is acutaway side view of the display system 100 cut along line 2C-2C ofFIGS. 2A and 2B. FIG. 2D is a portion 104 of the cutaway side view ofthe display system 100 as illustrated in FIG. 2D in greater detail.

Referring to FIGS. 1A through 2D, the display system 100 includes alighting system 110 adapted to provide light for a display panel 140. Inthe illustrated embodiment, a diffusant layer 130 which is a componentof lighting system is placed between the illuminating substrate 112 andthe display panel 140 to diffuse the light from the illuminatingsubstrate 112 before the light reaches the display panel 140. Thedisplay panel 140 includes a plurality of sub-layers to polarized,filter, and otherwise operates on the diffused light whereby a desiredpattern is lit and discernable from the front 101 of the display system100.

The display system 100 can have a wide range of lateral dimensions 106,108 depending on application and desired characteristics of the displaysystem 100. For example, the lateral dimensions 106, 108 can be in theorder of millimeters or in the order of meters or even beyond.

Lighting System

Continuing to refer to FIGS. 1A through 2D, the lighting system 110includes the illuminating substrate 112. The illuminating substrate 112has a first major surface 111 and a second major surface 113 and definesan array of mounting holes 114. To avoid clutter only two of elevenmounting holes 114 illustrated in FIG. 1B are pointed to with referencenumeral 114. An array of light emitting diode (LED) modules 150 occupythe mounting holes 114, one LED module 150 per mounting hole 114. Thatis, the array of LED modules 150 is affixed to the illuminatingsubstrate 112. Again, for clarity of discussion, only one LED module 150is illustrated in FIG. 1B thus more clearly illustrating the mountingholes 114; however, in actual application, each mounting hole 114 isoccupied by an LED module 150. In FIG. 1B, the LED module 150 isillustrated “floating” under the lighting system 110 to avoid obscuringthe illustrations of the mounting holes 114.

Illuminating Substrate

The illuminating substrate 112 includes a substrate core 118 which is,for example, an insulating layer of printed circuit board (PCB). Thesubstrate core 118 has a first major surface 117 and a second majorsurface 119 opposite the first major surface 117. A light reflectivelayer 120 covers a major portion of the first major surface 117 of thesubstrate core 118 forming an optically reflective surface 111 as thefirst major surface 111 of the illuminating substrate 112. The lightreflective layer 120 can be realized by application of opticallyreflective material such as, for example, metal silver (Ag), gold (Au),anodized aluminum (Al), or reflective material such as Barium Sulfate,Titanium Dioxide paint. The reflective surface 111 can be polished to aspecular finish. Alternatively, the reflective surface 111 canincorporate diffusing grating to promote dispersion and diffusion oflight reflecting on the reflective surface 111.

The illuminating substrate 112 includes circuit elements 124 on thesecond major surface 119 of the substrate core 118. The circuit elements124 can include, for example, electrically conductive traces fordelivery of electrical power, ground, and control signals to the LEDmodules 150. The circuit elements 124 can be made of copper or otherelectrically conductive material.

In the illustrated embodiment, the substrate core 118, the reflectivelayer 120, and the circuit elements 124 have thickness in the order of afew microns to a few millimeters depending on the application. Here, thecircuit elements 124 can be connection traces having a thickness in theorder of several microns. Neither the reflective layer 120 nor thecircuit elements 124 are allowed to cover-up the mounting holes 114 thusallowing mounting of the LED modules 150 through the illuminatingsubstrate 112.

The illuminating substrate 112 defines the array of mounting holes 114.The size of the array (thus the number of the mounting holes 114), theshape and the dimensions of each mounting hole 114, and the spacingdistance 115 between the mounting holes 114 depend on the desiredapplication and properties of the lighting system 100. In theillustrated example embodiment, each mounting hole 114 is generallycircular in shape with diameter ranging in the order of a few to severalmillimeters and is placed in a predetermined pattern. The shape, thesize, and the spacing of the mounting hole 114 can vary widely dependingon application. For example, the mounting holes 114 may have othershapes (rectangular, elliptical, or other suitable shapes), sizesranging in the order of millimeters or less to meters or more. Thespacing of the mounting holes 114 are determined by a plurality offactors such as, for example only, size of the mounting holes 114, heatdissipation requirements, and desired luminous intensity and totalluminous flux. In the illustrated embodiment, the mounting holes 114 arearranged within several millimeters from each other. Much, if not theentire lighting system 110 may be populated with these mounting holes114.

LED Modules

Each mounting hole 114 is occupied by the LED module 150. FIG. 3 is aperspective view of one embodiment of the LED module 150. FIG. 2Dillustrates, inter alia, a cut-away side view of the LED module 150 ofFIG. 3. Referring to FIGS. 2D and 3, the LED module 150 includes a LEDmodule body 152, a reflector cup portion 154, and a heat sink portion156. The module body 152 provides a supporting substrate for one or acluster of LED chips 160 which may be of different colors, for example,red, green and blue, attached to the module body 152. For convenienceonly one LED chip 160 is illustrated. The LED chip 160 represents one ormore LED chips.

A reflector cup portion 154 of the LED module 150 surrounds and definesa cavity 155 within which the LED chip 160 is mounted to the module body152. The reflector cup portion 154 defines an outer shape and outerdimensions that are substantially similar to the shape and thedimensions of the mounting holes 114. In the illustrated embodiment, theouter shape of reflector cup portion 154 is generally circular, and itsdiameter 157 is in the order of millimeters.

Electrically conductive traces 158 are provided on the module body 152to allow for electrical connection of the LED chip 160 to the circuitelements 124 of the illuminating substrate 112 when the LED module 150is mounted at a mounting hole 114. When the LED module 150 is mounted ata particular mounting hole 114, one or more conductive traces 158 of theLED module 150 connect with the circuit elements 124 of the illuminatingsubstrate 112. The conductive traces 158 are connected to the bottomside LED chip 160, top side of the LED chip 160 via bond wire 162, orboth. The LED chip 160 can be, for example only, from chemicals GaN forblue and green lights and AlGaAsP for Red.

After the placement of the LED chip 160, the bond wire 162, or both, thecavity 155 can be filled with encapsulant material such as, for example,soft thermo-set plastics such as, for example, silicone, epoxy, or acombination of these. The encapsulant material can include additionalmaterial such as, for example, wavelength shifting material such asphosphors to absorb light having a first wavelength and reemit the lightat a second wavelength. Further, the encapsulant material can includematerial to diffuse the light from the LED chip 160 for example, glass,titanium dioxide, barium sulfate, calcium carbonate, and other suitablematerial.

The LED modules 150 are mounted in the mounting holes 114 to allow lightto launch toward the diffusant layer 130, and eventually to the displaypanel 140. The LED modules 150 can be mounted in the mounting holes 114using solders, or any electrically conductive adhesive, such as, forexample, Ag-epoxy.

Heat Sink

When the LED chip 160 is activated, light and heat are generated by theLED chip 160. The heat spreads throughout the LED module 150. Much ofthe heat is dissipated by the heat sink 156 which can be an integralportion of, or attached to the module body 152 to increase the thermaldissipation capacity of the LED module 150 to an extend that noadditional heatsink is needed to dissipate heat generated by LEDs.

Diffusant Layer

Referring again to FIGS. 1A through 2D, in the illustrated embodiment,the diffusant layer 130, a component of the display system 100, isplaced between the illuminating substrate 112 and the display panel 140.The diffusant layer 130, though, is not necessary in all embodiments.The diffusant layer 130 can be made of transparent material such asglass or transparent plastics such as polycarbonate orPolymethylmethacrylate (PMMA) that is filled with small particles oflight reflective material, for example only, Barium Sulfate, TitaniumDioxide, or other suitable material. When an LED module 150 emits light,its light rays cover only a smaller area of the illuminating substrate.After passing through the diffusant layer, the light rays will cover amuch larger area, hence delivering a uniform luminance on the front faceof the diffusant layer for illuminating a display panel. In additional,phosphors may be added in the diffusant layer to absorb certainwavelengths of light and re-emit other wavelengths.

FIG. 2E is a simplified diagram of another portion of the display system100 of FIGS. 2A through 2D. Referring to FIG. 2E, the LED module 150emits light in a wide range of angles relative to the normal axis ofsecond major surface (back) 143 of the display panel 140. A firstportion of the emitted light illustrated by ray 131 is emitted at afirst angle 133 relative to normal (perpendicular) to the back 143 ofthe display panel 140 such that the light 131 is transmitted directlythrough the diffusant layer 130 into and beyond the display panel 140.This is when the first angle 133 is less than the TIR (Total InternalRefraction) angle presented by the back surface 143 of the display panel140.

A second portion of the emitted light illustrated by ray 134 is emittedat a second angle 135 relative to the back 143 of the display panel 140.The second angle 135 can be, in the present example, greater than theTIR (Total Internal Refraction) angle presented by the back surface 143of the display panel 140. In the illustrated embodiment, the secondportion 134 of the emitted light reflects off of a diffusant 137, thenoff the optically reflective surface 111 toward the back surface 143 ofthe display panel 140 at a third angle 138 less than the TIR angle. If,for example, the diffusant 137 were not present, the light ray 134 wouldhave an angle of incident on the back surface 143 at an angle greaterthan the critical angle, hence totally reflected from it. Subsequently,ray 134 may be trapped between the two surfaces and its luminousintensity be reduced by a small percentage at each reflection and theweaker ray 134 may eventually exit from the medium. As illustrated, thediffusant 137 reduces loss of light. Further, the diffusant 137 allowslight from an LED module to be scattered and spread out thus covering alarger area. This has the effect of mixing light from multiple LEDmodules. Accordingly, more uniform light is provided to the LED panel140.

Consequently, light from a plurality of LED modules 150 are mixed in thediffusant layer 130 as it interacts with the light scattering particlesand layer interfaces. Light reflected back toward the illuminatingsubstrate 112 is reflected back toward the display panel 140 by thereflective surface 111 of the illuminating substrate 112, henceconserving the photons emitted by the light sources.

Referring to FIGS. 2A through 2E, the diffusant layer 130 is placed indirect contact with the front face of illuminating substrate 112.Alternatively, as illustrated in the Figures, the diffusant layer 130can be optically coupled with the lighting system 110 by optical gel 132which can be Nye's soft silicone gel. The optical gel 132 may be filledwith phosphors or a diffusants. The optical gel 132 can have arefractive index that matches the refractive index of the diffusionlayer to minimize interface loss.

To minimize loss of light from the side edges of the diffusant layer130, the edges of the diffusant layer 130 may be specular finished andbeveled at an angle 139 such that light rays that hit at the edges arereflected at TIR (Total Internal Reflection) angle. Alternatively, thesurface 136 of the edges of the diffusant layer 130 can include areflective coating 136 realized by application of optically reflectivematerial such as, for example, silver (Ag), gold (Au), aluminum (Al), orany other reflective material such as Barium Sulfate, Titanium Dioxide.

Display Panel

Referring again to FIGS. 1A through 2D, in the illustrated embodiment,the display panel 140 has a first major surface 141 (its “front”) and asecond major surface 143 (its “back”). The display panel 140 is acontrollable and partially translucent display panel known in the art.For example, the display panel 140 can be a TFT (Thin Film Transistor)LCD (Liquid Crystal Display) type panel designed to work with backlightprovided by the lighting system 110. The display panel 140, as a TFT LCDpanel, includes a number of sub-layers. The display panel 140 includes afirst polarizing filter sub-layer, a thin film transistor sub-layer, aliquid crystal sub-layer, a color filter sub-layer, and a secondpolarizing filter sub-layer. Design and operations of these sub-layersand the TFT LCD panel 140 is known to those skilled in the art.

The lighting system 110 provides light proximal to the second majorsurface 143 of the display panel 140. The diffused light is provided tothe display panel 140. The sub-layers of the display panel 140 areconnected to, powered by, and controlled with various circuits (notillustrated) outside the display system 100 to operate on the lightentering the display panel 140 selectively allowing varying portions ofthe diffused light through the display panel 140. The result is that adesirable, viewable pattern or other information appears on the surface101 of the display system 100.

The display system 100 is applicable in a wide range of application suchas, for example only, displays of instruments and watches, computermonitors, television, bill boards, road signs, and commercialadvertisement displays.

CONCLUSION

From the foregoing, it will be apparent that the present invention isnovel and offers advantages over the current art. Although specificembodiments of the invention are described and illustrated above, theinvention is not to be limited to the specific forms or arrangements ofparts so described and illustrated. For example, differingconfigurations, sizes, or materials may be used to practice the presentinvention. The invention is limited by the claims that follow.

1. An illuminating substrate comprising: a first major surface; a secondmajor surface opposite the first major surface; a substrate core havinga first major core surface and a second major core surface opposite thefirst major core surface, the first major core surface being on a sameside of the substrate core as the first major surface of theilluminating substrate and the second major core surface being on a sameside of the substrate core as the second major surface of theilluminating substrate; and circuit elements disposed on the secondmajor core surface, the circuit elements comprising at least a portionof the second major surface of the illuminating substrate; and thesubstrate core and the circuit elements together defining at least onemounting hole through the illuminating substrate.
 2. The illuminatingsubstrate of claim 1 further comprising a light reflective layercovering at least a portion of the first major core surface of thesubstrate core.
 3. The illuminating substrate of claim 2 wherein thelight reflective layer comprises at least one member from a groupconsisting of silver, gold, aluminum, reflective paint, barium sulfate,and titanium dioxide.
 4. The illuminating substrate of claim 2 whereinthe light reflective layer comprise diffusion grating.
 5. Theilluminating substrate of claim 2 wherein the reflective layer comprisesat least a portion of the first major surface of the illuminatingsubstrate.
 6. The illuminating substrate of claim 1 wherein the at leastone mounting hole comprises an array of mounting holes.
 7. Theilluminating substrate of claim 6 further comprising an array of lightemitting diode (LED) modules, each module comprising an LED chip,wherein each of the modules is substantially adjacent to the secondmajor surface and forms an electrical connection with the circuitelements of the second major surface and at least a portion of each ofthe LED modules occupying a corresponding mounting hole of the array ofmounting holes.
 8. The illuminating substrate of claim 7 wherein each ofthe LED modules further comprises a reflector cup defining a cavity withthe LED chip of the respective LED module positioned within the cavity.9. The illuminating substrate of claim 8 wherein each of the reflectorcups defines an outer shape that fittingly affixes within thecorresponding mounting hole in the illuminating substrate.
 10. Theilluminating substrate of claim 7 wherein the LED module comprises atleast one LED chip and conductive traces connected to the LED chip. 11.The illuminating substrate of claim 10 wherein the circuit elements areadapted to connect to the conductive traces of the LED module.
 12. Theilluminating substrate of claim 7 wherein each LED module comprises acluster of LED chips, the LED chips emitting light at differentwavelengths or colors.
 13. The illuminating substrate of claim 1 furthercomprising a diffusant layer disposed over at least a portion of thefirst surface, the diffusant layer optically coupled to the firstsurface via an optical gel.
 14. The illuminating substrate of claim 13wherein the optical gel comprises phosphors.
 15. The illuminatingsubstrate of claim 13 wherein the diffusant layer comprises edges havinga reflective coating.
 16. The illuminating substrate of claim 13,wherein the optical gel comprises a material having a refractive indexequal to the refractive index of the diffusant layer.
 17. Theilluminating substrate of claim 1 wherein the circuit elements compriseconductive traces.
 18. The illuminating substrate of claim 1 wherein thefirst major core surface of the substrate core is adjacent at least aportion of the first major surface of the illuminating substrate.
 19. Alighting system comprising: an illuminating substrate comprising a firstmajor surface and a second major surface opposite the first majorsurface, the illuminating substrate comprising: a substrate core havinga first major core surface and a second major core surface opposite thefirst major core surface, the first major core surface being on a sameside of the substrate core as the first major surface of theilluminating substrate and the second major core surface being on a sameside of the substrate core as the second major surface of theilluminating substrate; circuit elements disposed on the second majorcore surface, the circuit elements comprising at least a portion of thesecond major surface of the illuminating substrate; and the substratecore and the circuit elements together defining a mounting hole throughthe illuminating substrate; and a light emitting diode (LED) module, themodule comprising an LED chip, wherein the module is substantiallyadjacent to the second major surface of the illuminating substrate andforms an electrical connection with the circuit elements of the secondmajor surface of the illuminating substrate and at least a portion ofthe LED module occupies the mounting hole.
 20. The lighting system ofclaim 19 further comprising a light reflective layer covering at least aportion of the first major core surface of the substrate core.
 21. Thelighting system of claim 20 wherein the light reflective layer comprisesat least one member from a group consisting of silver, gold, aluminum,reflective paint, barium sulfate, and titanium dioxide.
 22. The lightingsystem of claim 20 wherein the light reflective layer comprisesdiffusion grating.
 23. The lighting system of claim 20 wherein thereflective layer comprises at least a portion of the first major surfaceof the illuminating substrate.
 24. The lighting system of claim 19further comprising a heat sink.
 25. The lighting system of claim 19wherein the LED module comprises a cluster of LED chips, the LED chipsemitting light at two or more different wavelengths or colors.
 26. Thelighting system of claim 19 wherein the LED module comprises one or moreelectrically conductive traces and is substantially adjacent to thesecond major surface of the illuminating substrate such that the one ormore electrically conductive traces electrically connect with thecircuit elements of the second major surface of the illuminatingsubstrate.
 27. The lighting system of claim 19 wherein the LED modulefurther comprises a reflector cup defining a cavity with the LED chip ofthe LED module positioned within the cavity.
 28. The lighting system ofclaim 27 wherein the reflector cup of the LED module defines an outershape that fittingly affixes within the corresponding mounting hole inthe illuminating substrate.
 29. The lighting system of claim 19 whereinthe first major core surface of the substrate core is adjacent at leasta portion of the first major surface of the illuminating substrate.